Electron discharge device



Oct. 6, 1-959 .1. F. STEPHENS ELECTRON DISCHARGE DEVICE Filed April 291955 INVENTOR JOE F. STEPHENS Fatented Oct. 6, 1959 2,907,912 ELECTRONDISCHARGE DEVICE .loe F. Stephens, Owensboro, Ky., assigno'r to GeneralElectric Company, a corporation of New York Application April 29, 1955,Serial No. 504,957

4 Claims. (Cl. 313261) to minimize any inter-electrode leakage and,broadly considered, the present invention provides means to accomplishthese desirable ends.

' The primary object of my invention is to provide a new and improvedelectron discharge device having a high arc-over rating and lowinter-electrode leakage.

Another object of my invention is to provide new and improved electrodesupporting means for electron discharge devices.

Another object of my invention is to provide in an electron dischargedevice, a new and improved electrode supporting arrangement adapted forminimizing any tendency toward arc-over in the tube and for minimizinginter-electrode leakage.

Further objects and advantages of my invention will become apparent asthe following description proceeds and the, features of novelty whichcharacterize my invention will be pointed out with particularly in theclaims annexed to and forming part of this specification.

In carrying out the objects of my invention I provide an electrondischarge device including an envelope wherein is arranged spacedinsulative support assemblies between which are mounted a plurality ofelectrodes in closely spaced relation. The assemblies each comprise anapertured first insulative member having a slightly conductive coatingthereon and a second insulative mem ber secured across the aperture inthe first member and having a highly insulative coating. High potentialelectrodes of the device are mounted between the first insulativemembers and low potential electrodes are mounted between the secondinsulative members. The side edges of the second insulative members arespaced from the corresponding edges of the apertures in the firstmembers.

For a better understanding of my invention reference may be had to theaccompanying drawing in which:

Fig. 1 is a partially sectionalized elevational view of an electrondischarge device illustrating my invention;

Fig. 2 is a sectional view taken along the line 2-2 in Fig. 1 andlooking in the direction of the arrows;

Fig. 3 is an exploded perspective view illustrating an insulativesupport assembly of my invention; and

Fig. 4 is a partially sectionalized elevational view of a modified formof my support assembly.

Referring to the drawing I have shown in Fig. 1 an electron dischargedevice or tube designated 1 and of the type generally referred to as areceiving tube. The tube 1 includes an insulative envelope 2 wherein ishoused an assembly 3 generally referred to in the art as a tube cage.The tube cage comprises a plurality of electrode elements and mountingmeans therefor and will be described in more detail hereinafter.Suitably mounted atop the cage is a getter assembly generally designated4. This assembly may be of any construction well-known in the art andneed not be described in detail herein.

The tube 1 further includes an insulative base 5 carrying a plurality ofprongs 6 suitably electrically connected to conductive leads 7 whichextend in a sealed manner through the lower end of the envelope 2 forsupporting the cage 3 and making electrical connections with the variouselectrode elements thereof. Additionally, the base 5 includes a bayonetplug 8 adapted for facilitating insertion and orientation of the prongs6 in the receptacles of a tube socket (not shown). Suitably mounted onthe envelope opposite the base 5 is a conductive top cap 9 adapted formaking electrical connection through a conductive lead 9a to anelectrode in the cage 3.

The cage 3 includes a cathode 10 which may be of the indirectly heatedtype shown and comprise a sleeve 11 having a suitable electron emissivecoating 12 and a heating element or filament 13 therein; or,alternatively, the cathode may be of the directly heated type wellknownin the art. The cathode 10 is adapted for being electrically connectedby a tab 14 to one of the leads 7 while the ends of the filament 13 areeach adapted for being similarly connected to an appropriate one of theleads 7. Further included in the cage structure is a grid 15 comprisinga pair of spaced support rods 16, one of which is adapted for beingsuitably electrically connected to one of the leads 7, and a helicallywound grid wire 17. For purposes of simplification of illustration onlyone grid 15 is shown. However, it will be understood that any desirednumber of such electrodes could be provided in the illustrated type oftube. Further, it will readily seem that the novel features of myinvention can be utilized in other tube types than the single coaxialarrangement shown, as for example multiple-unit tubes such as doublediodes, triodes and the like, or combinations thereof.

Also included in the particular tube type shown, and perhaps better seenin Fig. 2, is a beam deflection plate 18 which comprises a spaced pairof vertical portions 19 of substantially U-shaped cross sectioninterconnected by a plurality of horizontal portions 20. The beamdeflection plate 18 is adapted for being suitably electrically connectedto an appropriate .pair of the leads 7.

Another electrode included in the cage 3 is an anode 21 which may betubular and of any desired cross-sectional configuration. Additionally,the anode in the illustrated tube type is the electrode adapted forbeing electrically connected by the above-mentioned leads 9a to the topcap 9. During normal operation of the tube 1, the anode 21 is subject torelatively high peak positive pulse voltages and, therefore, shall behereinafter re: ferred to as the high potential electrode or element.cathode 10, grid 15 and beam deflection plate 18 operate at relativelylow potentials and shall hereinafter be referred to collectively as thelow potential electrodes or elements.

It will be clear from the drawing that the various electrodes arecoaxially arranged in closely spaced relation and are adapted for beingmounted by the extension of end portions thereof through insulativesupport structures.

Now, as mentioned above, the anode 21 is subject to high peak-valuedpositive voltage pulses during normal tube operation. This operatingcondition togetherwith The I the relative close electrode spacinggenerally results in a tendency toward arc-over and interelectrodeleakage, especially at surface portion of the electrode supportstructure.

My invention contemplates the provision of a tube structure includinginsulative support arrangements or assemblies particularly adapted forminimizing arc-over thereby to increase the arc-over rating of the tubeand for minimizing inter-electrode leakage. As seen in Figs. 1-3, I haveprovided a pair of spaced insulative support assemblies 25, one assemblyfor the upper cage support and the other for the lower cage support.These assemblies may be identically arranged or, if desired, theorientation of the elements of the assemblies can be reversed, accordingas the assembly is used for top or bottom cage support, as will appear.

As perhaps best seen in Fig. 3, each assembly 25 includes an insulativefirst member or disk 26 which may be formed of mica or any suitableinsulative material. Additionally, in accordance with common practice,the disks 26 may be further formed to include circumferentially spacedpoints 27 to facilitate the fitting thereof transversely in the envelope2 in the manner shown in Figs. 1 and 2. The disk 26 is provided with acoating indicated by 28 in Fig. 3, the substance and purpose of whichwill be brought out in detail hereinafter.

Provided in the center of each disk 26 is an enlarged aperture 29 whichmay be hexagonal, as shown, or of any other configuration which provideselongated opposite side edges 30. Outwardly spaced from the side edges30 are apertures 31 adapted for receiving tabs 32 formed off oppositelyextending lateral extensions of the anode 21. Thus, the disks 26 areadapted for having the relatively high potential element or anode 21mounted therebetween in the manner shown in Fig. 1.

Provided for being secured across the apertures 29 of the disks 26 inthe manner shown in Figs. 1 and 2, as by the use of eyelets 33 or anysuitable securing means, is an elongated insulative second member orstrip 34-. The strip 34 is provided with a coating, indicated by 35 inFig. 3, the substance and purpose of which will also be brought out indetail hereinafter. The strip 34 may also be formed of mica or anysuitable insulative material and is narrower in width than the distancebetween the edges 30 of the aperture 29 in the disk 26. The relativedimensioning of the strip 34 and the aperture 29 results in theprovision of elongated spaces or openings, designated 36 in Fig. 2, oneither side of the strip, the purpose for which will be brought out indetail hereinafter.

Additionally, the strips 34 are each formed to include a centralelongated aperture 37 for receiving an end of the cathode 1G, a spacedpair of apertures 38 for receiving end portions of the grid rods 16, anda second pair of spaced apertures 39 for receiving tabs 40 formed offthe beam deflection plate 18. As seen in Fig. l, the tabs 40 on thelower portion of the plate 18 are adapted for extending through theapertures 39 and for being suitably electrically connected, as bywelding, to a shield member 41 which in turn is similarly connected to apair of the leads 7. Thus, is provided the above-referred-to electricalconnection between the plate 18 and the appropriate ones of the leads 7.In the just-described manner the strips 34 of the top and bottom supportassemblies are adapted for having the relatively low potential elements,or elements other than the anode 21, mounted coaxially therebetween.

The arrangement described above results in minimizing the probability ofarc-over between the relatively high and low-potential elements wherebya high arcover rating for the tube 1 can be assigned and further,minimizes any inter-electrode leakage between the low potentialelements. The high arc-over rating thus obtained is due in part to themounting of the high and low potential elements in separate insulativemembers located in different planes which results in physical andelectrical isolation of the high potential element with respect to thelow potential elements and the abrupt discontinuity or interruption ofthe surface of the insulation between the high and low potentialelements.

The high arc-over rating is further due to the abovereferred-to coating28 on the disks 26. The coating 28 is formed of any material and to athickness which will adapt it for being slightly conductive at therelatively high peak positive voltage pulses to which the high potentialelement of the tube is subjected during normal operation. The coating 28is effective for minimizing the tendency toward arc-over or increasingthe arc-over rating inasmuch as it affords the anode potential a highresistance leakage path which allows the potential to be distributedover the entire areas of the disks 26, thereby to prevent the buildup oraccumulation of any electric charge of arcing magnitude on any singleportion of the disks. I have found sodium silicate and potassiumsilicate to be suitable materials for forming the coating 28. Thesematerials have been found particularly suitable since, in addition tobeing slightly conductive at the relatively high potentials, theyrequire no binders, they have surface textures which particular ly adaptthem for use as coating materials, and they do not tend to poison oraffect deleteriously oxide coated cathodes. It is to be understood,however, that my invention is not limited to the use of the aboveenumerated materials. Any type of coating may be used which will presenta slightly conductive or very high resistivity conduction path to theflow of electric current between the high and low potential elements.

Still further, the tendency toward arc-over at the electrode supportassemblies 25 is minimized by the elongated spaces or openings 36provided by the particular configurations of the disks 26 and strips 34comprising the support assemblies.

As seen in Fig. 4 the arc path over each of the assemblies 25 and,therefore, the arc-over rating of the tube, may be further increased byspacing the disks 26 and their respective strips 34. This may besuitably accomplished by the use of elongated eyelets 42 having suitableinsulative spacers 43 fitted thereon and disposed between the disks 26and the strips 34.

The inter-electrode leakage between the low potential electrodes orelements is minimized by the abovereferred-to coating 35 on the strips34. The coating 35 is formed of any material and to a thickness whichwill adapt it for being highly insulative or resistive to the relativelylow potential currents tending to flow between the electrodes in thestrips 34 across the surface portions of the strips. Materials which aresuitable for forming the coating 35 are aluminum oxide, magnesium oxide,and zirconium oxide. These materials, in addition to being highlyresistive to current flow between the relatively low potential elementsmounted between the strips 34, are particularly suitable inasmuch as thesurface textures and adherence properties thereof particularly adaptthem for use as coating materials, and'they also do not tend to poisonoxide coated cathodes. It is to be understood that this feature of myinvention also is not to be limited to the enumerated coating materials.Any type of coating material may be used on the strips 34 which will behighly insulative or resistive to the flow of electric current betweenthe relatively low potential electrodes.

Thus it will be seen that I have provided an electron discharge deviceadapted for having a high arc-over rating and minimal inter-electrodeleakage. Additional- 1y, I have provided electrode supporting meanswhich is adapted for increasing the arc-over rating of a tube'andminimizing inter-electrode leakage and is particularly adapted formanufacture through use of mass production techniques.

For example, the mica disks 26 may be drum-sprayed or otherwise coatedin volume with a solution including any of the above-referred-toslightly conductive materials. As mentioned above no binder is requiredwith these materials. Similarly the strips 34 may be sprayed with asolution including a highly insulative material. Preterably a suitablebinder such as gum arabic or nitro cellulose is used with these lattermaterials. Thereafter, these elements may all be even baked to dry themand remove any traces of any coating material binders thereby to leavethe elements suitably coated with the desired materials. From the bakingoven the coated elements may go to an assembly station whereat they arefastened or secured together as by use of the eyelets 33 or 42 and inthe manners shown in the drawing.

While I have shown and described specific forms of my invention, I donot desire my invention to be limited to the particular forms shown anddescribed and I intend by the appended claims to cover all modificationswithin the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In an electron discharge device including an evacuated envelope and aplurality of electrode elements co axially arranged in said envelope andincluding at least one adapted for high potential operation, means forsupporting said electrode elements in said envelope and adapted forminimizing arc-over between said elements comprising; an insulative diskhaving an elongated aperture and an insulative strip carried by saiddisk, said strip being narrower than said aperture and extendinglongitudinally across the middle of said aperture whereby laterallyextending elongated slots are provided in said support means on eitherside of said strip, said disk being further apertured for havingportions of the high potential element extend therethrough at pointslaterally disposed relative to said strip and slots, said strip beingapertured for having portions of the other of said elements extendingtherethrough, and a coating of material selected from the groupconsisting of sodium silicate and potassium silicate on said diskproviding a high resistivity conduction path effective for distributingany electrical charges on said disk.

2. In an electron discharge device including an evacuated envelope and aplurality of electrode elements coaxially arranged in said envelope andincluding at least one adapted for high potential operation, means forsupporting said electrode elements in said envelope and adapted forminimizing arc-over between said electrodes and any inter-electrodeleakage comprising; an insulative disk having an elongated aperture, andan insulative strip carried by said disk, said strip being narrower thansaid aperture and extending longitudinaly across the middle of saidaperture whereby laterally extending slots are provided in said supportmeans on either side of said strip, said disk being further aperturedfor having portions of the high potential element extend therethrough atpoints laterally disposed relative to said strip and slots, said stripbeing apertured for having portions of the other of said elementsextending therethrough and a coating of material selected from the groupconsisting of aluminum oxide, magnesium oxide and zirconium oxide onsaid strip adapted for resisting any current flow across said strip.-

3. In an electron discharge device including an evacuated envelope and aplurality of electrode elements coaxially arranged in said envelope andincluding at least one adapted for high potential operation, means forsupporting said electrode elements in said envelope and adapted forminimizing arc-over between said elements and minimizing anyinter-electrode leakage comprising; an insulative disk having anelongated aperture and an insulative strip carried by said disk, saidstrip being narrower than said aperture and extending longitudinallyacross the middle of said aperture whereby laterally extending slots areprovided in said support means on either side of said strip, said diskbeing further apertured for having portions of the high potentialelement extend therethrough at points laterally disposed relative tosaid strip and slots, said strip being apertured for having portions ofthe other of said elements extending therethrough, a coating of materialselected from the group consisting of sodium silicate and potassiumsilicate on said disk providing a high resistivity conduction patheffective for distributing any electrical charges on said disk, and acoating of materialselected from the group consisting of aluminum oxide,magnesium oxide and zirconium oxide on said strip adapted for resistingany current flow across said strip.

4. In an electron discharge device including an evacuated envelope and aplurality of electrode elements mounted in said envelope and includingat least one adapted for high potential operation, means for supportingsaid electrode elements in said envelope and adapted for minimizingarc-over between said elements comprising; an insulative disk having anenlarged, elongated aperture, an insulative strip carried by said disk,said strip being narrower than said aperture and extendinglongitudinally across said aperture, thereby to provide laterallyextending spacesbetween the side edges of said strip and thecorresponding side edges of said aperture, said disk being furtherapertured outwardly of said spaces for having the high potential elementextend therethrough at points laterally separated from said strip bysaid spaces, said strip being apertured for having the other electrodeelements extend therethrough, said disk having a coating ofhigh-resistivity conductive material efiective for distributing anyelectrical charges on said disk, and said strip having a coating ofhighly insulative material effective for resisting any current flowacross said strip.

References Cited in the file of this patent UNITED STATES PATENTS1,558,883 Housekeeper Oct. 27, 1925 2,030,930 Parker Feb. 18, 19362,057,115 Rothe Oct. 13, 1936 2,077,814 Taylor Apr. 20, 1937 2,087,327McNally July 20, 1937 2,664,519 I Ishler Dec. 29, 1953 2,760,100Klopping Aug. 21, 1956

